1. Field of the Invention
This invention relates to the field of radio frequency identification (RFID) devices, and methods of making RFID devices.
2. Description of the Related Art
Radio frequency identification (RFID) tags and labels (collectively referred to herein as “devices”) are widely used to associate an object with an identification code. RFID devices generally have a combination of antennas and analog and/or digital electronics, which may include for example communications electronics, data memory, and control logic. For example, RFID tags are used in conjunction with security locks in cars, for access control to buildings, and for tracking inventory and parcels. Some examples of RFID tags and labels appear in U.S. Pat. Nos. 6,107,920, 6,206,292, and 6,262,692.
As noted above, RFID devices are generally categorized as labels or tags. RFID labels are RFID devices that are adhesively or otherwise have a surface attached directly to objects. RFID tags are secured to objects by other means, for example by use of a plastic fastener, string, or other fastening means.
RFID devices involve electrical connections between chips, antennas, and interposers that are used in some cases to facilitate electrical connection of the chips to the antennas. Such connections have been made using a variety of methods. Examples of such methods in flip chip bonding are: using conductive adhesives, which tend to be expensive, as well as plating processes, which can be expensive and difficult to implement; and ultrasonic welding, which has often been used in wire bonding and rarely in flip chip bonding, where it is difficult to integrate with other production processes. It will be appreciated that improvements are possible in RFID devices, in particular in view of the continued desirability to reduce costs of such devices.